The present invention relates generally to liquid level detection systems and, more particularly, to a system for accurately measuring the depth of liquid contained within the vessel and a method for operating such a sensor.
Certain substances, which are in a gaseous state at normal atmospheric temperature and pressure, are advantageously stored under higher than atmospheric pressure in high strength vessels. The advantage of such storage is that such substances liquefy under a suitably high pressure and therefore occupy less volume thereby requiring correspondingly less storage space. Substances, which have these thermodynamic properties, include propane LPG and at lowered temperatures natural gas (sometimes referred to as liquefied natural gas or LNG), both of which are used in home heating and industrially. In each of these applications, storage of the gas in a minimum of space is desirable. Containers capable of maintaining the necessary elevated pressure and in some cases reduced temperatures for these materials include cylindrical vessels with dished closed ends fabricated using materials such as aluminum or steel.
Ever increasing demands for the efficient management of these materials make accurate measurement of propane or (LNG) natural gas, in a container desirable. A suitably accurate measurement may be obtained by determining ratio of the volume of liquid and vapor in the container. The volume of liquid can be readily determined from its depth since the interior geometry and volume of the aforementioned storage vessel is fixed.